You can download LTspice XVII installer from Linear Technlogy Web site.
Click “Download LTspice XVII for Windwos 7,8 and 10” on the link page, then you can get the installer.
The first step of installation is “License Agreement and Disclaimer”.
If you can agree “License Agreement and Disclaimer”, click “Accept”. After clicking “Accept”, you can install LTspice XVII on your computer by clicking “Install Now”.
Finally “LTspice XVII has been successfully installed” dialog is displayed, and click “OK” to finish.
LTspice XVII window is opened after the installation.